Wireless power transfer system and wireless power transfer method

ABSTRACT

A wireless power transfer system includes a plurality of power sources and at least one power receiver, in which power transfer from the power sources to the power receiver is performed in wireless by using magnetic field resonance or electric field resonance. In the system, one of the plurality of power sources is designated as a master power source and the other one or more power sources are designated as slave power sources. In addition, the master power source controls the plurality of power sources and the at least one power receiver to perform the power transfer. This allows the system to perform the power transfer in an optimum state.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.14/492,375, filed on Sep. 22, 2014, which is a continuation applicationof International Patent Application No. PCT/JP2013/059107, filed on Mar.27, 2013, which claims the benefit of priority of prior Japanese PatentApplication No. 2012-074001, filed on Mar. 28, 2012 and prior JapanesePatent Application No. 2012-171261, filed on Aug. 1, 2012, the entirecontents of each of which are incorporated herein by reference.

FIELD

Embodiments discussed herein relate to a wireless power transfer systemand a wireless power transfer method.

BACKGROUND

In recent years, wireless power transfer techniques have been gainingattention in order to provide power supply or perform charging. Researchand development are being conducted regarding a wireless power transfersystem wirelessly performing power transfer to various electronicapparatuses such as mobile terminals and notebook computers andhousehold electrical appliances or to power infrastructure equipment.

In order to use wireless power transfer, it is preferable to standardizeso that no problem occurs in the use of a power source of a power sourceand a power receiver of a power receiver that are of differentmanufactures.

Among conventional wireless power transfer techniques, a technique usingelectromagnetic induction and a technique using radio waves havegenerally been known. On the other hand, expectations for power transfertechniques using magnetic field resonance (magnetic resonance) orelectric field resonance have been increasing recently, as techniquesallowing for power transfer to a plurality of power receivers and powertransfer to various three-dimensional postures while maintaining somedistance between power sources and the power receivers. Electric fieldresonance may also be called electric resonance.

As described above, attention has conventionally been paid to wirelesspower transfer techniques for wirelessly transferring power for thepurposes of power supply or charging. Nevertheless, standardization ofpower transfer techniques, for example, using magnetic field resonanceor electric field resonance has not been made so far.

There has thus been a concern over stagnation of practical applicationof a power transfer system using magnetic field resonance or electricfiled resonance or of a power source and a power receiver.

A variety of wireless power transfer techniques have conventionally beenproposed.

-   Patent document 1: Japanese Laid-open Patent Publication No.    2010-239769-   Patent document 2: U.S. Pat. No. 7,825,543-   Non-Patent document 1: SHOKI Hiroki, et al., “Standardization Trends    on Wireless Power transfer”, Technical Report of The Institute of    Electronics Information, and Communication Engineers (IEICE    technical report), WPT 2011-19, December 2011.

SUMMARY

According to an aspect of the embodiments, there is provided a wirelesspower transfer system that includes a plurality of power sources and atleast one power receiver, power transfer from the power sources to thepower receiver being performed in wireless by using magnetic fieldresonance or electric field resonance.

In the wireless power transfer system, one of the plurality of powersources is designated as a master power source and the other one or morepower sources are designated as slave power sources. The master powersource controls the plurality of power sources and the at least onepower receiver to perform the power transfer.

The object and advantages of the invention will be realized and attainedby means of the elements and combinations particularly pointed out inthe claims.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and arenot restrictive of the invention.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram schematically depicting one example of awireless power transfer system according to an embodiment of the presentinvention;

FIG. 2A is a diagram (1) for illustrating a modified example of atransmission coil in the wireless power transfer system of FIG. 1;

FIG. 2B is a diagram (2) for illustrating a modified example of thetransmission coil in the wireless power transfer system of FIG. 1;

FIG. 2C is a diagram (3) for illustrating a modified example of thetransmission coil in the wireless power transfer system of FIG. 1;

FIG. 3A is a circuit diagram (1) depicting an example of an independentresonance coil;

FIG. 3B is a circuit diagram (2) depicting an example of the independentresonance coil;

FIG. 3C is a circuit diagram (3) depicting an example of the independentresonance coil;

FIG. 3D is a circuit diagram (4) depicting an example of the independentresonance coil;

FIG. 4A is a circuit diagram (1) depicting an example of a resonancecoil connected to a load or a power supply;

FIG. 4B is a circuit diagram (2) depicting an example of the resonancecoil connected to the load or the power supply;

FIG. 4C is a circuit diagram (3) depicting an example of the resonancecoil connected to the load or the power supply;

FIG. 4D is a circuit diagram (4) depicting an example of the resonancecoil connected to the load or the power supply;

FIG. 5A is a diagram (1) for illustrating an example of controlling amagnetic field by a plurality of power sources;

FIG. 5B is a diagram (2) for illustrating an example of controlling amagnetic field by the plurality of power sources;

FIG. 5C is a diagram (3) for illustrating an example of controlling amagnetic field by the plurality of power sources;

FIG. 6A is a diagram (1) for illustrating correspondence between aplurality of power sources and a plurality of power receivers;

FIG. 6B is a diagram for illustrating a state of each power receiver inFIG. 6A;

FIG. 6C is a diagram (2) for illustrating correspondence between theplurality of power sources and the plurality of power receivers;

FIG. 6D is a diagram (3) for illustrating correspondence between theplurality of power sources and the plurality of power receivers;

FIG. 6E is a diagram (4) for illustrating correspondence between theplurality of power sources and the plurality of power receivers;

FIG. 6F is a diagram (5) for illustrating correspondence between the anda plurality of power sources and the plurality of power receivers;

FIG. 7 is a diagram for illustrating posture information of powerreceivers;

FIG. 8A is a diagram (1) for illustrating distribution control of powerto a plurality of power receivers;

FIG. 8B is a diagram (2) for illustrating distribution control of powerto the plurality of power receivers;

FIG. 8C is a diagram (3) for illustrating distribution control of powerto a plurality of power receivers;

FIG. 8D is a diagram (4) for illustrating distribution control of powerto the plurality of power receivers;

FIG. 8E is a diagram (5) for illustrating distribution control of powerto the plurality of power receivers;

FIG. 8F is a diagram (6) for illustrating distribution control of powerto the plurality of power receivers;

FIG. 8G is a diagram (7) for illustrating distribution control of powerto the plurality of power receivers;

FIG. 8H is a diagram (8) for illustrating distribution control of powerto the plurality of power receivers;

FIG. 9 is a diagram for illustrating human detection and outputadjustment for a power source;

FIG. 10 is a diagram for illustrating a status of each power receiver inFIG. 9;

FIG. 11 is a diagram for illustrating measures for a power receiver witha battery residual capacity of zero;

FIG. 12A is a diagram (1) for illustrating a synchronization problem ina plurality of power sources;

FIG. 12B is a diagram (2) for illustrating the synchronization problemin the plurality of power sources;

FIG. 12C is a diagram (3) for illustrating the synchronization problemin the plurality of power sources;

FIG. 13A is a diagram (1) for illustrating a first synchronizationmethod against the synchronization problem in the plurality of powersources;

FIG. 13B is a diagram (2) for illustrating the first synchronizationmethod against the synchronization problem in the plurality of powersources;

FIG. 13C is a diagram (3) for illustrating the first synchronizationmethod against the synchronization problem in the plurality of powersources;

FIG. 14A is a diagram (1) for illustrating a second synchronizationmethod against the synchronization problem in the plurality of powersources;

FIG. 14B is a diagram (2) for illustrating the second synchronizationmethod against the synchronization problem in the plurality of powersources;

FIG. 14C is a diagram (3) for illustrating the second synchronizationmethod against the synchronization problem in the plurality of powersources;

FIG. 15A is a diagram (1) for illustrating a synchronizationpattern-mixed communication applied to the second synchronization methodillustrated with reference to FIG. 14A to FIG. 14C;

FIG. 15B is a diagram (2) for illustrating the synchronizationpattern-mixed communication applied to the second synchronization methodillustrated with reference to FIG. 14A to FIG. 14C;

FIG. 15C is a diagram (3) for illustrating the synchronizationpattern-mixed communication applied to the second synchronization methodillustrated with reference to FIG. 14A to FIG. 14C;

FIG. 15D is a diagram (4) for illustrating the synchronizationpattern-mixed communication applied to the second synchronization methodillustrated with reference to FIG. 14A to FIG. 14C;

FIG. 16 is a block diagram depicting one example of the wireless powertransfer system of the embodiment;

FIG. 17 is a block diagram depicting one exemplary power source in thewireless power transfer system of FIG. 16;

FIG. 18 is a block diagram depicting one exemplary power receiver in thewireless power transfer system of FIG. 16;

FIG. 19 is a flowchart for illustrating a first example of processing inthe wireless power transfer system of the embodiment;

FIG. 20 is a flowchart for illustrating a second example of processingin the wireless power transfer system of the embodiment;

FIG. 21 is a flowchart for illustrating a third example of processing inthe wireless power transfer system of the embodiment;

FIG. 22 is a flowchart for illustrating a fourth example of processingin the wireless power transfer system of the embodiment;

FIG. 23 is a flowchart for illustrating the fourth example of processingin the wireless power transfer system of the embodiment; and

FIG. 24 is a flowchart for illustrating a fifth example of processing inthe wireless power transfer system of the embodiment.

DESCRIPTION OF EMBODIMENTS

Hereinafter, a detailed description will be given of embodiments of awireless power transfer system and a wireless power transfer method withreference to the attached drawings. FIG. 1 is a block diagramschematically depicting one example of a wireless power transfer systemaccording to an embodiment of the present invention.

In FIG. 1, reference sign 1 denotes a primary side (a power source:power source), and reference sign 2 denotes a secondary side (a powerreceiver: power receiver). As depicted in FIG. 1, the primary side 1includes a wireless power transfer unit 11, a high frequency powersupply unit 12, a power transfer control unit 13, and a communicationcircuit unit (a first communication circuit unit) 14. In addition, thesecondary side 2 includes a wireless power reception unit 21, a powerreception circuit unit 22, a power reception control unit 23, and acommunication circuit unit (a second communication circuit unit) 24.

The wireless power transfer unit 11 includes a first coil (a powersupply coil) 11 b and a second coil (an LC resonator) 11 a, and thewireless power reception unit 21 includes a third coil (an LC resonator)21 a and a fourth coil (a power extraction coil) 21 b.

As depicted in FIG. 1, the primary side 1 and the secondary side 2perform energy (electric power) transmission from the primary side 1 tothe secondary side 2 by magnetic field resonance (electric fieldresonance) between the LC resonator 11 a and the LC resonator 21 a.Power transfer from the LC resonator 11 a to the LC resonator 21 a canbe performed not only by magnetic field resonance but also electricfield resonance or the like. However, the following description will begiven mainly by way of example of magnetic field resonance.

The primary side and the secondary side communicate with each other(near field communication) by the communication circuit unit 14 and thecommunication circuit unit 24. A distance of power transfer (a powertransfer range PR) by the LC resonator 11 a of the primary side and theLC resonator 21 a of the secondary side is set to be shorter than adistance of communication (a communication range CR) by thecommunication circuit unit 14 of the primary side 1 and thecommunication circuit unit 24 of the secondary side 2 (PR<CR).

In addition, power transfer by the LC resonators 11 a and 21 a isperformed by a system (an out-band communication) independent fromcommunication by the communication circuit units 14 and 24.Specifically, power transfer by the LC resonators 11 a and 21 a uses,for example, a frequency band of 6.78 MHz, whereas communication by thecommunication circuit units 14 and 24 uses, for example, a frequencyband of 2.4 GHz. The communication by the communication circuit units 14and 24 can use, for example, a DSSS wireless LAN system based on IEEE802.11b or Bluetooth (registered trademark).

The wireless power transfer system of the present embodiment performspower transfer using magnetic field resonance or electric fieldresonance by the resonator 11 a of the power source 1 and the LCresonator 21 a of the power receiver 2, for example, in a near field ata distance of about a wavelength of a frequency used. Accordingly, therange of power transfer (a power transfer area) PR varies with thefrequency used for power transfer.

The high frequency power supply unit 12 supplies power to the powersupply coil (the first coil) 11 b, and the power supply coil 11 bsupplies power to the LC resonator 11 a arranged very close to the powersupply coil 11 b by using electromagnetic induction. The LC resonator 11a transfers power to the LC resonator 21 a (the secondary side 2) at aresonance frequency that causes magnetic field resonance between the LCresonators 11 a and 21 a.

The LC resonator 21 a supplies power to the power extraction coil (thefourth coil) 21 b arranged very close to the LC resonator 21 a, by usingelectromagnetic induction. The power extraction coil 21 b is connectedto the power reception circuit unit 22 to extract a predetermined amountof power. The power extracted from the power reception circuit unit 22is used, for example, for charging a battery in the battery unit 25, asa power supply output to the circuits of the secondary side 2, or thelike.

The high frequency power supply unit 12 of the primary side 1 iscontrolled by the power transfer control unit 13, and the powerreception circuit unit 22 of the secondary side 2 is controlled by thepower reception control unit 23. Then, the power transfer control unit13 and the power reception control unit 23 are connected through thecommunication circuit units 14 and 24 and adapted to perform variouscontrols so that power transfer from the primary side 1 to the secondaryside 2 can be performed in an optimum state.

FIG. 2A to FIG. 2C are diagrams for illustrating modified examples of atransmission coil in the wireless power transfer system of FIG. 1. FIG.2A and FIG. 2B depict exemplary three-coil structures, and FIG. 2Cdepicts an exemplary two-coil structure.

In other words, in the wireless power transfer system depicted in FIG.1, the wireless power transfer unit 11 includes the first coil 11 b andthe second coil 11 a, and the wireless power reception unit 21 includesthe third coil 21 a and the fourth coil.

On the other hand, in the example of FIG. 2A, the wireless powerreception unit 21 is set as a single coil (an LC resonator) 21 a, and inthe example of FIG. 2B, the wireless power transfer unit 11 is set as asingle coil (an LC resonator) 11 a.

Further, in the example of FIG. 2C, the wireless power reception unit 21is set as a single LC resonator 21 a and the wireless power transferunit 11 is set as a single LC resonator 11 a. FIG. 2A to FIG. 2C aremerely examples and, obviously, various modifications can be made.

FIG. 3A to FIG. 3D are circuit diagrams depicting examples of anindependent resonance coil (the LC resonator 21 a), and FIG. 4A to FIG.4D are circuit diagrams depicting examples of a resonance coil (the LCresonator 21 a) connected to a load or a power supply. FIG. 3A to FIG.3D correspond to the LC resonator 21 a of FIG. 1 and FIG. 2B, and FIG.4A to FIG. 4D correspond to the LC resonator 21 a of FIG. 2B and FIG.2C.

In the examples depicted in FIG. 3A and FIG. 4A, the LC resonator 21 aincludes a coil (L) 211, a capacitor (C) 212, and a switch 213 connectedin series, in which the switch 213 is ordinarily in an off-state. In theexamples depicted in FIG. 3B and FIG. 4B, the LC resonator 21 a includesthe coil (L) 211 and the capacitor (C) 212 connected in series, and theswitch 213 connected in parallel to the capacitor 212, in which theswitch 213 is ordinarily in an on-state.

In the examples depicted in FIG. 3C and FIG. 4C, the LC resonator 21 aof FIG. 3B and FIG. 4B includes the switch 213 and the resistance (R)214 connected in series and arranged in parallel to the capacitor 212,in which the switch 213 is ordinarily in the on-state.

The examples of FIG. 3D and FIG. 4D depict the LC resonator 21 a of FIG.3B and FIG. 4B, in which the switch 213 and another capacitor (C′) 215connected in series are arranged in parallel to the capacitor 212, andthe switch 213 is ordinarily in the on-state.

In each of the LC resonators 21 a described above, the switch 213 is setto “off” or “on” so that the LC resonator 21 a does not operateordinarily. The reason for this is, for example, to prevent heatgeneration or the like caused by power transfer to a power receiver notin use (on the secondary side) 2 or to a power receiver 2 out of order.

In the above structure, the LC resonator 11 a of the primary side (powersource) 1 can also be set as in FIG. 3A and FIG. 3D and FIG. 4A to FIG.4D. However, the LC resonator 11 a of the power source 1 may be set soas to operate ordinarily and may be controlled to be turned on/off by anoutput of the high frequency power supply unit 12. In this case, in theLC resonator 11 a, the switch 213 is to be short-circuited in FIG. 3Aand FIG. 4A.

In this manner, when a plurality of power receivers 2 are present,selecting only the LC resonator 21 a of a predetermined power receiver 2for receiving power transmitted from the power source 1 and making theLC resonator 21 a operable enables power to be transferred to theselected power receiver 2.

FIG. 5A to FIG. 5C are diagrams for illustrating examples of controllinga magnetic field by a plurality of power sources. In FIG. 5A to FIG. 5C,reference signs 1A and 1B denote power sources, and reference sign 2denotes a power receiver. As depicted in FIG. 5A, an LC resonance coil11 aA for power transfer used for magnetic field resonance of the powersource 1A and an LC resonance coil 11 aB for power transfer used formagnetic field resonance of the power source 1B are arranged, forexample, so as to be orthogonal to each other.

Additionally, the LC resonance coil 21 a used for magnetic fieldresonance of the power receiver 2 is arranged at a different angle (anangle not parallel) at a position surrounded by the LC resonance coil 11aA and the LC resonance coil 11 aB.

The LC resonance coil 11 aA and the LC resonance coil 11 aB for powertransfer may also be provided in a single power source. In other words,a single power source 1 may include a plurality of wireless powertransfer units 11. However, the following description will mainlydescribe a system in which a single power source 1 includes a singlewireless power transfer unit 11 (LC resonance coil 11 a).

Although details will be given later, designating one of the pluralityof power sources as a master and the other one or more power sources asslaves means that the calculation processing unit (CPU) of the singlemaster power source controls all the LC resonators included in themaster power source and the slave power sources.

FIG. 5B depicts a situation in which the resonance coil 11 aA and theresonance coil 11 aB output an in-phase magnetic field, and FIG. 5Cdepicts a situation in which the resonance coil 11 aA and the resonancecoil 11 aB output a reverse phase magnetic field.

As can be seen above, when power is transferred to the power receiver 2positioned at an arbitrary position and an arbitrary posture (angle) bythe plurality of power sources 1A and 1B, magnetic fields occurring inthe resonance coils 11 aA and 11 aB of the power sources 1A and 1Bchange variously.

In other words, the wireless power transfer system of the presentembodiment includes a plurality of power sources and at least one powerreceiver and adjusts outputs (strengths and phases) between theplurality of power sources according to positions (X, Y, and Z) andpostures (θx, θy, and θz) of the power receiver.

FIG. 6A is a diagram (1) for illustrating correspondence between aplurality of power sources and a plurality of power receivers, and FIG.6B is a diagram for illustrating a status of each of the power receiversin FIG. 6A, in which two power sources 1A and 1B and five powerreceivers 2A to 2E are arranged.

In the wireless power transfer system of the present embodiment, thesingle power source 1A of the plurality of power sources 1A and 1B isdesignated as a master (primary) and the other power source 1B isdesignated as a slave (secondary). For example, the master (the powersource 1A) determines processing such as optimization of the pluralityof power sources and the power receiver.

In FIG. 6A, reference sign PRa denotes a power transfer area of thepower source 1A (a master power transfer area); reference sign PRbdenotes a power transfer area of the power source 1B (a slave powertransfer area); reference sign CRa denotes a communication area of thepower source 1A (a master communication area); and reference sign CRbdenotes a communication area of the power source 1B (a slavecommunication area).

Accordingly, statuses of the power receivers 2A to 2E are as follows.Specifically, as depicted in FIG. 6B, the power receiver 2A is outsidethe master communication area CRa (x), outside the slave communicationarea Crb, outside the master power transfer area PRa, and outside theslave power transfer area PRb, and simply waits for communication fromthe power sources.

Next, the power receiver 2B is located within the master communicationarea CRa (∘), outside the slave communication area CRb, outside themaster power transfer area PRa, and outside the slave power transferarea PRb. Thus, communicating with the master power source 1A allows fora confirmation that the power receiver 2B is outside the power areas(outside the master and slave power transfer areas).

In addition, the power receiver 2C is within the master communicationarea CRa, within the slave communication area CRb, outside the masterpower transfer area PRa, and outside the slave power transfer area PRb.Thus, communicating with the master and slave power sources 1A and 1Ballows for a confirmation that the power receiver 2C is outside thepower areas.

In addition, the power receiver 2D is within the master communicationarea CRa, within the slave communication area CRb, within the masterpower transfer area PRa, and outside the slave power transfer area PRb.Thus, communicating with the master and slave power sources 1A and 1Ballows for a confirmation that the power receiver 2D is within the powerarea of the power source 1A (within the master power transfer area PRa).

Additionally, the power receiver 2E is within the master communicationarea CRa, within the slave communication area CRb, within the masterpower transfer area PRa, and within the slave power transfer area PRb.Thus, communicating with the master and slave power sources 1A and 1Ballows for a confirmation that the power receiver 2E is within the powerareas of the power sources 1A and 1B (within the power transfer areasPRa and PRb).

Of the plurality of power sources, a single power source is determinedas a master. The master may be determined, for example, depending on acondition in which a largest number of power receivers are locatedwithin the communication area of the power source or within the powertransfer area thereof, as described later.

For example, when there is an equal condition in which each one powerreceiver is located within the communication areas of the power sources,the master may be determined by adding an additional condition such as acommunication strength between the power source and the power receiver,or an arbitrary one power source may be determined as a master using arandom number table or the like.

When the power sources are of different manufacturers, optimizationrules for strengths and phases of the power sources differ from eachother. Thus, in the wireless power transfer system of the embodiment,designating one of the plurality of power sources as a master allows themaster power source to control optimization for the power sourcesincluding the other one or more slave power sources.

FIG. 6C to FIG. 6E are diagrams (2 to 4) for illustrating correspondencebetween the plurality of power sources and the plurality of powerreceivers, and illustrating how to determine a master and slaves in theplurality of power sources.

First, a master power source and slave power sources are determined inthe plurality of power sources when the power sources are located withincommunication ranges (communication areas) of each other, power transferranges (power transfer areas) of the power sources overlap each other,and the relevant power receiver detects the overlapping of the powertransfer areas.

Specifically, FIG. 6C depicts a situation in which the communicationarea CRa of the power source 1A overlaps the communication area CRb ofthe power source 1B, whereas the power transfer area PRa of the powersource 1A does not overlap the power transfer area PRb of the powersource 1B. In this situation, since the power transfer areas PRa and PRbdo not overlap each other, both the power sources 1A and 1B aredesignated as respective master power sources.

Next, FIG. 6D depicts a situation in which the communication area CRaand the power transfer area PRa of the power source 1A overlap thecommunication area CRb and the power transfer area PRb of the powersource 1B and the power receiver 2 is included in both the powertransfer areas PRa and PRb.

In the situation of FIG. 6D, the power sources 1A and 1B are locatedwithin the communication areas CRa and CRb of each other, the powertransfer areas PRa and PRb overlap each other, and moreover, the powerreceiver 2 detects the overlapping of the power transfer areas PRa andPRb.

Accordingly, in FIG. 6D, one (1A) of the power sources 1A and 1B isdesignated as a master power source and the other one (1B) thereof isdesignated as a slave power source. In this case, although the powersource 1B may be designated as a master and the power source 1A may bedesignated as a slave, either one of the power sources 1A and 1B isdesignated as a master power source.

In addition, FIG. 6E depicts a situation in which the power sources 1Aand 1B are arranged in the same positional relationship as that in FIG.6D described above, but the power receiver 2 is not present (not locatedwithin the communication areas CRa and CRb). In this situation, both thepower sources 1A and 1B are designated as masters.

Similarly, when three or more power sources are arranged, for example,in the positional relationship corresponding to FIG. 6D, any one of thepower sources is designated as a master power source. Various methodscan be considered to designate a single master power source from theplurality of power sources. One example of the methods will be describedwith reference to FIG. 6F.

FIG. 6F is a diagram (5) for illustrating correspondence between the anda plurality of power sources and the plurality of power receivers, inwhich four power sources 1A to 1D are arranged in a line. Acommunication area CRa of the power source 1A includes the power source1B but does not include the power sources 1C and 1D. Similarly, acommunication area CRd of the power source 1D includes the power source1C but does not include the power sources 1A and 1B.

In addition, a communication area CRb of the power source 1B includesthe power sources 1A and 1C but does not include the power source 1D.Similarly, a communication area CRc of the power source 1C includes thepower sources 1B and 1D but does not include the power source 1A.

In the situation of FIG. 6F, for example, the power source 1B isdesignated as a mater (a master power source) and the other powersources 1A, 1C, and 1D are designated as slaves (slave power sources).Alternatively, the power source 1C may be designated as a master.Meanwhile, designating the power source 1B as a master power sourcemakes it difficult to directly communicate with the power source 1D. Inthis case, the power source 1B communicates with the power source 1D viathe power source 1C to control optimization and the like.

Thus, in the wireless power transfer system of the present embodiment,it is preferable to designate, as a master, a power source that candirectly communicate with a largest number of power sources whendesignating a single master from a plurality of power sources.

In FIG. 6F, the four power sources 1A to 1D are arranged in a straightline. However, practically, a plurality of power sources will bedisposed in various positional relationships, for example, by beingembedded in a wall or a ceiling of a room, being built in a desk or atable, or being mounted on a floor, a table, or the like.

FIG. 7 is a diagram for illustrating posture information of powerreceivers and depicts a power source 1A as a master and two powerreceivers 2′ and 2″. Examples of the power receiver 2 may include a2-dimensional charge power receiver 2′ charged only with two-dimensionalpositional information (X, Y, Z) and a 3-dimensional charge powerreceiver 2″ charged with three-dimensional position information (X, Y,Z) and posture information (θx, θy, θz).

In other words, the power receiver (2D) 2′ is charged, for example, bymounting (horizontally mounting) on an upper surface of the powersource, and the power receiver (3D) 2″ is charged, for example, even atan arbitrary position and an arbitrary posture with respect to the powersource.

Accordingly, even when the wireless power transfer system of theembodiment includes the 2-dimensional charge power receiver 2′ and the3-dimensional charge power receiver 2″ together, the system can performappropriate power transfer processing. The posture information (θx, θy,θz) used for 3-dimensional charging is available, for example, from athree-dimensional acceleration sensor or the like incorporated even inthe current power receiver 2″, such as a smart phone.

FIG. 8A to FIG. 8D are diagrams (1 to 4) for illustrating distributioncontrol of power to a plurality of power receivers, in whichdistribution control without resonance adjustment of LC resonators isillustrated. In FIG. 8A to FIG. 8D, for simplifying the illustration,only one power source 1 is depicted, although the same applies also to aplurality of power sources. In addition, efficiency means a powertransfer efficiency between the power source 1 (the LC resonator 11 a)and the power receiver 2 (the LC resonator 21 a).

First, as depicted in FIG. 8A, when two power receivers 2A and 2B whosereceived powers are equal (for example, 5 W) are horizontally mounted onthe power source 1 to perform 2-dimensional charging, for example,efficiencies with respect to the power receivers 2A and 2B are equal(for example, 80%). Thus, in the situation of FIG. 8A, a simultaneouspower transfer mode (simultaneous transmission mode) can be performed inwhich power transfer to the two power receivers 2A and 2B issimultaneously performed.

Next, as depicted in FIG. 8B, when the two power receivers 2A and 2Bwhose received powers are equal (5 W) are arranged above the powersource 1 to perform 3-dimensional charging, for example, an efficiencywith respect to the power receiver 2A is 60% and an efficiency withrespect to the power receiver 2B is 80%.

In FIG. 8B, the reason why the efficiencies of the power receivers 2Aand 2B are different is that, for example, the power receivers 2A and 2Bhave different distances (positions) and different postures with respectto the power source 1. Accordingly, in the situation of FIG. 8B, thesimultaneous transmission mode is not applicable. Thus, power transferby a time division power transfer mode (a time division mode) isperformed, in which the power receiver 2A and charging to the powerreceiver 2B are charged by dividing time.

When simultaneous transmission mode is possible (for example, thesituation of FIG. 8A), time division mode is obviously possible. Inaddition, during charging (power transfer) to the power receiver 2A in atime division mode, the LC resonator 21 aB of the power receiver 2B isturned off, and conversely, during charging to the power receiver 2B,the LC resonator 21 aA of the power receiver 2A is turned off.

Additionally, as depicted in FIG. 8C, when the two power receiver 2A and2C whose received powers are different are horizontally mounted on thepower source 1 to perform 2-dimensional charging, for example,efficiencies with respect to the power receiver 2A and 2B are equal.

However, for example, while the received power of the power receiver 2Asuch as a smart phone is 5 W, the received power of the power receiver2C such as a notebook computer is 50 W, so that the received powers aredifferent between the power receivers 2A and 2C. Even in the situationof FIG. 8C, simultaneous transmission mode is not applicable, similarlyto FIG. 8B, so that power transfer by a time division mode is performed.

Furthermore, as depicted in FIG. 8D, for example, when the powerreceiver 2A with the received power of 5 W and the power receiver 2Cwith the received power of 50 W are arranged above the power source 1 toperform 3-dimensional charging, for example, an efficiency with respectto the power receiver 2A is 60% and an efficiency with respect to thepower receiver 2C is 80%. Accordingly, even in the situation of FIG. 8C,similarly to FIG. 8B and FIG. 8C, simultaneous transmission mode is notapplicable and thus power transfer by a time division mode is performed.

FIG. 8E to FIG. 8H are diagrams (5 to 8) for illustrating distributioncontrol of power to a plurality of power receivers, in whichdistribution control in resonance adjustment of LC resonators isillustrated. FIG. 8E to FIG. 8H correspond to FIG. 8A to FIG. 8Ddescribed above.

First, the power source 1 transmits power to a power receiver having alargest received power between or among the plurality of power receivers(for example, the notebook computer 2C having a received power of 50 W).In this situation, regarding the power receivers whose received powersare not the largest (for example, smart phones 2A and 2B having areceived power of 5 W), adjustment of LC resonators 21 aA and 21 aB ismade such that the power receivers 2A and 2B have an optimum receivedpower (5 W).

Specifically, adjustment (resonance adjustment) in the power receivers2A and 2B whose received powers are not the largest is made by changingresonance frequencies or Q values of the LC resonators 21 aA and 21 aBthereof so that the values of power received by the LC resonators 21 aAand 21 aB are suitable to the received powers of the power receivers 2Aand 2B.

Performing the resonance adjustment described above allows powertransfer to be performed in both of simultaneous transmission mode andtime division mode in all the situations of FIG. 8E to FIG. 8H. Forexample, in the situation of FIG. 8F, shifting a resonance frequency ora Q value of the LC resonator 21 aB of the power receiver 2B from anappropriate value allows for simultaneous transmission of power to thepower receivers 2A and 2B.

In addition, in the situations of FIG. 8G and FIG. 8H, shifting aresonance frequency or a Q value of the LC resonator 21 aA of the powerreceiver 2A from an appropriate value in both situations thereof allowsfor simultaneous transmission of power to the power receivers 2A and 2C.In addition, an application associated with the resonance adjustmentdescribed above has separately been filed by the same applicant as namedherein. However, it is obvious that the resonance adjustment of theinvention is not limited thereto and other methods are also applicable.

The master power source 1 performs the pieces of processing in FIG. 8Ato FIG. 8D and FIG. 8E to FIG. 8H, i.e., control of the strength andphase of power to be transmitted in the power source 1 and controls inthe respective power receivers 2A to 2C. In addition, although only thesingle power source 1 is depicted in FIG. 8A to FIG. 8D and FIG. 8E toFIG. 8H, a single master power source designated from a plurality ofpower sources usually performs each of the pieces of processingdescribed above.

FIG. 9 is a diagram for illustrating human detection and outputadjustment for a power source, and FIG. 10 is a diagram for illustratinga state of each power receiver in FIG. 9. In FIG. 9, reference sign SRadenotes a detection range (a bio-sensing range: a human detection sensorrange or a human detection sensor area) by a human detection sensor (abiodetection sensor (S2)) that detects the presence or absence of aperson (a living body) by the power source 1A.

A power transfer area (power transfer range) PRa of the power source 1Ahas, for example, a radius of from about 2 to about 3 meters. A humandetection sensor area SRa thereof is, for example, larger than the powertransfer area PRa and has a radius of from about 4 to about 5 m, and acommunication area (communication range) CRa thereof has a radius ofabout 10 m.

In other words, the human detection sensor area SRa is larger than thepower transfer area PRa and the communication area CRa is larger thanthe human detection sensor area SRa, so that a relationship ofPRa<SRa<CRa is established. The power transfer area PRa, the humandetection sensor area SRa, and the communication area CRa are merelyexamples, and obviously, various changes can be made depending onspecifications of the device.

Accordingly, statuses of the power receivers 2A to 2D are as follows.Specifically, as depicted in FIG. 10, the power receiver 2A is locatedoutside the communication area CRa of the power source 1A (x), outsidethe human detection sensor area SRa thereof, and outside the powertransfer area PRa thereof, and thus simply waits for communication fromthe power source.

Next, the power receiver 2B is located within the communication area CRa(∘), outside the human detection sensor area SRa, and outside the powertransfer area PRa, so that communicating with the power source 1A allowsfor a confirmation that the power receiver 2B is outside the power areaPRa.

Additionally, the power receiver 2C is located within the communicationarea CRa, within the human detection sensor area SRa, and outside thepower transfer area PRa, so that communicating with the power source 1Aallows for a confirmation that the power receiver 2C is outside thepower area PRa. Additionally, the power receiver 2D is located withinthe communication area CRa, within the human detection sensor area SRa,and within the power transfer area PRa, so that communicating with thepower source 1A allows for a confirmation that the power receiver 2D iswithin the power area PRa, and confirmation by the human detectionsensor can also be made.

A description will be given of an example of controlling output of thepower source 1A using a human detection sensor. For example, when noperson (no living body) is present in the human detection sensor areaSRa, a power transfer output from the power source 1A is set to, forexample, 50 W. Conversely, when a person is present in the humandetection sensor area SRa, the power transfer output from the powersource 1A is reduced to, for example, 5 W.

FIG. 11 is a diagram for illustrating measures for a power receiver witha battery residual capacity of zero. First, in order to obtain necessarypower information of a power receiver, communication between a powersource and a power receiver is essential. However, for example,communication is impossible when the battery residual capacity of thepower receiver is zero.

Then, instead of performing power transfer (power reception) to thepower receiver 2D (2) with the battery residual capacity of zero byusing the wireless power reception unit 21 (LC resonator 21 a), forexample, the power receiver 2D (2) may be charged by electromagneticinduction using the power extraction coil 21 b while keeping the LCresonator 21 a in an off state. This is effective when the wirelesspower reception unit 21 of the power receiver 2 includes the LCresonator 21 a and the power extraction coil 21 b, i.e., in thesituations of FIG. 1 and FIG. 2B.

Alternatively, it is also possible to charge by electromagneticinduction using the LC resonator 21 a being in the off state. In thiscase, the LC resonator 21 a of FIG. 4A and the LC resonator 21 a of FIG.4C, which are open in the off state, will be excluded.

The reason for excluding the LC resonator 21 a of FIG. 4C is that aresistance 214 has a resistance value significantly larger than aconnection resistance of the power reception circuit unit 22 and thusreceived power is consumed by the resistance 214.

FIG. 11 depicts a situation in which the power source (master powersource) 1A is performing power transfer to the plurality of powerreceivers 2B and 2C, in which the power receiver 2D with the batteryresidual capacity of zero is arranged in contact with a predeterminedposition of the power source 1A and a battery residual capacity zeromode of the power source 1A is designated.

In the designation of the battery residual capacity zero mode in thepower source 1A, for example, when a battery residual capacity zeroswitch arranged on the power source 1A is turned on, the power source 1Astops power transfer (power transfer) to the power receivers 2B and 2C.

Furthermore, the power source 1A turns off resonance of the LCresonators 21 a (21 aA to 21 aC) of the power receivers 2A to 2C locatedwithin the communicable communication area CRa. Power transfer to thepower receiver 2A is originally not performed and the LC resonator 21 aAis already off.

This allows power transfer using electromagnetic induction (coupling) tobe performed only for the power receiver 2D with the battery residualcapacity of zero but not to be performed for the other power receivers2A to 2C.

Then, in the power receiver 2D with the battery residual capacity ofzero, battery charging is done by, for example, power transfer usingelectromagnetic induction and then the charging is continued untilcommunication between the power source 1A and the power receiver 2Dbecomes possible.

Charging processing for the power receiver 2D with the battery residualcapacity of zero by the power source 1A may be controlled so as to beperformed until communication with the power receiver 2D is recovered bygradually increasing power, for example, like test power transfer→smallpower transfer→medium power transfer. In addition, power transfer usingordinary magnetic field resonance is performed after the communicationbetween the power source 1A and the power receiver 2D has becomepossible. Obviously, power transfer using electromagnetic induction maybe performed until the battery of the power receiver 2D is sufficientlycharged.

FIG. 12A to FIG. 12C are diagrams for illustrating a synchronizationproblem in a plurality of power sources, in which the diagramsillustrate a frequency synchronization problem in deviation betweenmagnetic resonance frequencies used for power transfer in two powersources 1A [power transfer system 1] and 1B [power transfer system 2].

As depicted in FIG. 12A to FIG. 12C, a frequency of the high frequencypower supply unit 12B of the power source 1B deviates by Δf from afrequency f of the high frequency power supply unit 12A of the powersource 1A (f+Δf), a beat occurs in the power receiver 2 that havereceived power transfer from the two power sources 1A and 1B.

In other words, the LC resonator 21 a of the power receiver 2 resonateswith a magnetic field of the frequency f from the LC resonator 11 aA ofthe power source 1A and a magnetic field of the frequency (f+Δf) fromthe resonator 11 aB of the power source 1B to receive power.

In this situation, even when Δf is about a few hertz, an output of theLC resonator 21 a of the power receiver 2 includes the beat, as depictedin FIG. 12B and FIG. 12C. Then, the output of the LC resonator 21 aincluding the beat is input to the battery unit 25 through the powersupply circuit 22.

Specifically, when the frequency from the LC resonator 11 aA of thepower source 1A is 10 M [Hz] and the frequency from the LC resonator 11aB of the power source 1B is 10 M+1 [Hz], a beat of 1 [Hz] occurs.

Thus, regardless of how highly precise the oscillator may be, it isdifficult to avoid the occurrence of a beat as long as the LC resonators11 aA and 11 aB are controlled asynchronously, leading to reduction inpower transfer efficiency (for example, reduction to a half or less).

As a result, power transmitted to the power receiver 2 is significantlyreduced. In other words, when a plurality of power transfer sources arepresent, a synthesized magnetic field generates a beat even when drivingfrequencies deviate slightly, which significantly reduces power transferefficiency.

Such a difference between the resonant frequencies of the power sources1A and 1B occurs, for example, due to an element to be used and amanufacturing stage, an ambient temperature of the power sources 1A and1B arranged, or other factors.

FIG. 13A to FIG. 13C are diagrams for illustrating a firstsynchronization method against the synchronization problem in theplurality of power sources. FIG. 13A depicts a situation in which, forexample, the two power sources 1A and 1B are distant from each other anddo not simultaneously transmit power to the same power receiver (2).FIG. 13B and FIG. 13C depict a situation in which, for example, the twopower sources 1A and 1B are close to each other and transmit power tothe same power receiver (2).

As depicted in FIG. 13A to FIG. 13C, the power sources 1A and 1Brespectively include oscillators 121A and 121B, amplifiers 122A and122B, PLL (Phase Locke Loop) circuits 210A and 210B, and two switchesSW11A, SW12A and SW11B, SW12B, respectively.

The circuits 210A and 210B are not limited to PLL circuits, and circuitscapable of controlling synchronization (synchronization circuits), forexample, such as DLL (Delay Locked Loop) circuits, can be applied fromwide choices. In addition, the oscillators 121A and 121B may be circuitsusing quartz or synchronization circuits such as PLL circuits.

First, as depicted in FIG. 13A, for example, when the two power sources1A and 1B are distant from each other and power transfer areas of eachother do not overlap, in other words, when the two power sources 1A and1B do not simultaneously transmit power to the same power receiver (2),the power sources 1A and 1B, respectively, are designated as primaryones.

Specifically, without synchronization processing, the primary powersources 1A and 1B, respectively, amplify frequencies of the respectiveoscillators 121A and 121B by the amplifiers 122A and 122B and output theamplified frequencies to transmit power independently.

Next, with reference to FIG. 13B and FIG. 13C, a description will begiven of a situation in which the two power sources 1A and 1Bsimultaneously transmit power to the same power receiver (2). This is,for example, a situation in which the two power sources 1A and 1B areclose to each other or one of the power sources 1A and 1B starts outputand the output overlaps an output of the other one thereof. One of thepower sources (for example, 1A) is designated as a primary one and theother power source (for example, 1B) is designated as a secondary one.

FIG. 13B and FIG. 13C will illustrate an example using the two powersources 1A and 1B. However, even when three or more power sources arearranged, similarly, one of the power sources is designated as a primaryone and the remaining power sources are designated as secondary ones.

In designation of the power sources as a primary or secondary one, forexample, the above-described master power source may be designated as aprimary power source and the above-described one or more slave powersources may be designated as secondary power sources. Alternatively,designation of the primary and secondary power sources may be madeindependently.

Specifically, for example, one of slaves may be designated as a primarypower source, and the other one or more slaves and the master may bedesignated as secondary power sources. In FIG. 13B and FIG. 13C, 1A isdesignated as a primary power source and 1B is designated as a secondarypower source.

As depicted in FIG. 13B, when synchronization is started, the primarypower source 1A continues output at a frequency of the own oscillator121A thereof. In this situation, the secondary power source 1B causesthe switch SW11B to disconnect the own oscillator 121B thereof from theown amplifier 122B thereof to stop output.

At the same time, the secondary power source 1B connects the LCresonator 11 aB (power transfer coil) with the PLL circuit 210B by theswitch SW12B to receive power (power reception) from the LC resonator 11aA of the primary power source 1A by the LC resonator 11 aB. In otherwords, the secondary power source 1B uses the LC resonator 11 aB thathas stopped power transfer as an antenna receiving an output signal ofthe primary power source 1A.

During the synchronization processing of the secondary power source 1B,for example, the output level of the primary power source 1A may bechanged so as to be lowered for synchronization. Additionally, duringthe synchronization processing, for example, charging of all powerreceivers as power transfer destinations is preferably stopped byinstruction of the master power source. When stopping the charging ofthe power receivers, the resonator system (LC resonator) of each powerreceiver is preferably turned off.

Thus, in the primary power source 1A, the oscillation frequency of theoscillator 121A thereof is used for synchronization, so thatsynchronization processing-related instructions are obviously controlledaccording to the instruction of the master power source.

The PLL circuit 210B of the secondary power source 1B performs phasesynchronization (frequency tracking) with respect to the frequency ofthe oscillator 121A of the primary power source 1A according to a signalreceived by the LC resonator 11 aB. The PLL circuit 210B tracks and thenlocks the frequency. As a result, the PLL circuit 210B of the secondarypower source 1B outputs a signal (clock) having a frequency synchronizedwith the frequency of the oscillator 121A of the primary power source1A.

Furthermore, as depicted in FIG. 13C, after completion of thesynchronization of the PLL circuit 210B, the switch SW 12B cuts theconnection between the LC resonator 11 aB and the PLL circuit 210B andthe switch SW11B connects the PLL circuit 210B and the amplifier 122B.In this way, the secondary power source 1B restarts power transfer bythe output signal of the PLL circuit 210B synchronized with thefrequency of the oscillator 121A of the primary power source 1A.

Accordingly, the first synchronization method can prevent the occurrenceof a beat in the LC resonator 21 a of the power receiver 2 receivingpower from both the power sources 1A and 1B by matching the drivingfrequencies of the LC resonators 11 bA and 11 bB of the power sources 1Aand 1B.

Driving frequency adjustment (synchronization processing) in thesecondary power source 1B is preferably repeated, for example, at apredetermined time interval of from about a few minutes to about a fewtens of minutes in order to compensate for changes due to an ambienttemperature of the power sources 1A and 1B arranged, or other factors.

FIG. 14A to FIG. 14C are diagrams for illustrating a secondsynchronization method against the synchronization problem in theplurality of power sources. FIG. 14A depicts a situation in which, forexample, the two power sources 1A and 1B are distant from each other anddo not simultaneously transmit power to the same power receiver (2),whereas FIG. 14B and FIG. 14C depict a situation in which, for example,the two power sources 1A and 1B are close to each other and transmitpower to the same power receiver (2).

As depicted in FIG. 14A to FIG. 14C, the power sources 1A and 1Brespectively include oscillators 121A and 121B, amplifiers 122A and122B, PLL circuits 220A and 220B, communication circuit units(short-distance communication circuits) 14A and 14B, and switches 13Aand 13B, respectively. The circuits 220A and 220B are not limited to PLLcircuits and, for example, may be synchronization circuits capable ofcontrolling synchronization, such as DLL circuits, as described above.

The first synchronization method described with reference to FIG. 13A toFIG. 13C uses the LC resonator 11 aB of the secondary power source 1B asthe antenna to synchronize the frequency of the PLL circuit 210B of thesecondary power source 1B with the frequency of the oscillator 121A ofthe primary power source 1A.

On the other hand, the second synchronization method that will bedescribed with reference to FIG. 14A to FIG. 14C uses the communicationcircuit unit 14A of the primary power source 1A and the communicationcircuit unit 14B of the secondary power source 1B to performsynchronization control of the frequency of the PLL circuit 220B of thesecondary power source 1B.

First, as depicted in FIG. 14A, for example, when the two power sources1A and 1B are distant from each other and power transfer areas of eachother do not overlap, in other words, when the two power sources 1A and1B do not simultaneously transmit power to the same power receiver (2),the power sources 1A and 1B respectively transmit power as primary powersources.

In other words, without synchronization processing, the primary powersources 1A and 1B amplify the frequencies of the respective oscillators121A and 121B by the amplifiers 122A and 122B and outputs thefrequencies to transmit power independently. This is the same as in FIG.13A described above.

Next, with reference to FIG. 14B and FIG. 14C, a description will begiven of a situation in which the two power sources 1A and 1Bsimultaneously transmit power to the same power receiver (2). This is,for example, a situation in which the two power sources 1A and 1B areclose to each other or one of the power sources starts output and theoutput overlaps an output of the other power source. One of the powersources (for example, 1A) is designated as a primary one and the otherone thereof (for example, 1B) is designated as a secondary one.

FIG. 14B and FIG. 14C illustrate an example of the two power sources 1Aand 1B. However, even when three or more power sources are arranged, oneof the power sources is designated as a primary power source and theremaining power sources are designated as secondary power sources.

In addition, as described above, in designation of a primary powersource and secondary power sources, for example, the master power sourcemay be a primary power source and the one or more slave power sourcesmay be secondary power sources. Alternatively, designation of theprimary and secondary power sources may be made independently.

As depicted in FIG. 14B, when synchronization is started, the primarypower source 1A continues output at a frequency of the own oscillator121A thereof and outputs a synchronization pattern obtained from theoscillator 121A through the communication circuit unit 14A.

In this situation, the secondary power source 1B causes the switch SW13Bto cut off the connection between the own oscillator 121B thereof andthe own amplifier 122B thereof to stop output. It is enough to stop theoutput of the secondary power source 1B only during the initialsynchronization processing in which the PLL circuit 220B is synchronized(tracked) with the frequency of the oscillator 121A of the primary powersource 1A and then connected with the amplifier 122B.

In other words, after that, it is unnecessary to stop the output of thesecondary power source 1B during synchronization processing performedfor a second time and thereafter in which the PLL circuit 220B of thesecondary power source 1B is synchronized with the frequency of theoscillator 121A of the primary power source 1A (for example, at a timeinterval of from about a few minutes to about a few tens of minutes).

A radio signal including the synchronization pattern of the oscillator121A output from the communication circuit unit 14A of the primary powersource 1A is received by the communication circuit unit 14B of thesecondary power source 1B, and the synchronization of the oscillator121A is output to the PLL circuit 220B of the secondary power source 1B.

The PLL circuit 220B of the secondary power source 1B performs phasesynchronization (frequency tracking) with respect to the frequency ofthe oscillator 121A of the primary power source 1A according to thesynchronization pattern of the oscillator 121A received by thecommunication circuit unit 14B. As a result, the frequency of the PLLcircuit 220B of the secondary power source 1B is synchronized with thefrequency of the oscillator 121A of the primary power source 1A andlocked at the frequency.

As a result, the PLL circuit 220B of the secondary power source 1Boutputs a signal having the frequency synchronized with the frequency ofthe oscillator 121A of the primary power source 1A.

Maintaining the output level of the primary power source 1A at a usuallevel during the synchronization processing of the secondary powersource 1B allows the primary power source 1A to continue power transferto the power receiver (2).

In addition, in the initial synchronization processing in which the PLLcircuit 220B of the secondary power source 1B is synchronized and thenconnected with the amplifier 122B, it is preferable, for example, tostop charging of all power receivers as power transfer destinations byinstruction of the master power source. When stopping the charging ofthe power receivers, the resonance system (LC resonator) of each powerreceiver is preferably turned off.

Furthermore, as depicted in FIG. 14C, after completion of thesynchronization of the PLL circuit 220B, the switch SW13B connects thePLL circuit 220B with the amplifier 122B. As a result, the secondarypower source 1B restarts power transfer by the output signal of the PLLcircuit 220B synchronized with the frequency of the oscillator 121A ofthe primary power source 1A.

In the secondary power source 1B, it is only in the initialsynchronization processing that the PLL circuit 220B after havingcompleted the synchronization is connected with the amplifier 122B.During synchronization processing performed for a second time andthereafter, frequency synchronization is performed while maintaining theconnection between the PLL circuit 220B and the amplifier 122B.

In this manner, the second synchronization method can prevent theoccurrence of a beat in the LC resonator 21 a of the power receiver 2receiving power from both the power sources 1A and 1B by matching thedriving frequencies of the resonators 11 bA and 11 bB of the powersources 1A and 1B.

Driving frequency adjustment (synchronization processing for a secondtime and thereafter) in the secondary power source 1B is preferablyrepeated, for example, at a predetermined time interval of from about afew minutes to about a few tens of minutes in order to compensate forchanges due to an ambient temperature of the power sources 1A and 1Barranged, or other factors.

FIG. 15A to FIG. 15D are diagrams for illustrating a synchronizationpattern-mixed communication applied to the second synchronization methoddescribed with reference to FIG. 14A to FIG. 14C. FIG. 15A depicts animage (concept) of a radio signal output from the communication circuitunit 14A of the primary power source 1A, and FIG. 15B depicts an imageof a radio signal received by the communication circuit unit 14B of thesecondary power source 1B.

In addition, FIG. 15C depicts an image of a signal before modulationinput to the communication circuit unit 14A of the primary power source1A, and FIG. 15D depicts a radio signal input to the communicationcircuit unit 14B (demodulation circuit 140B) of the secondary powersource 1B and a demodulation signal.

First, as depicted in FIG. 15A, in the primary power source 1A, thecommunication circuit unit 14A outputs a signal having a wirelesscommunication frequency (for example, 2.4 GHz) in which a patternsynchronized with a frequency of the oscillator 121A (for example, 10MHz) is mixed.

In other words, the communication circuit unit 14A of the primary powersource 1A performs a synchronization pattern-mixed communication withthe communication circuit unit 14B of the secondary power source 1B. Thefrequency, the wireless communication frequency, and the like of theoscillator 121A are not limited to 10 MHz and 2.4 GHz and variousfrequencies can be applied.

Furthermore, as depicted in FIG. 15B, in the secondary power source 1B,the communication circuit unit 14B receives the signal having thewireless communication frequency in which the synchronization pattern ismixed and outputs a synchronization pattern SP indicating the frequencyof the oscillator 121A and a synchronization signal SWS indicating avalid range thereof.

Then, the frequency of the PLL circuit 220B of the secondary powersource 1B is synchronized with the frequency of the oscillator 121A ofthe primary power source 1A according to the synchronization pattern SPand the synchronization window signal SWS and locked at the frequency(for example, 10 MHz). As a result, the PLL circuit 220B of thesecondary power source 1B outputs a signal having the frequencysynchronized with the frequency of the oscillator 121A of the primarypower source 1A.

The synchronization pattern mixed in the signal having the wirelesscommunication frequency can be any as long as the pattern includesinformation that transmits a synchronization frequency (the frequency ofthe oscillator 121A of the primary power source 1A). The synchronizationpattern does not necessarily have to be a repetitive pattern of anactual synchronization frequency (or a frequency obtained by multiplyingor dividing the frequency by a constant).

For example, as depicted in FIG. 15C, in the primary power source 1A,the communication circuit unit 14A (modulation circuit) modulates asynchronization pattern-mixed signal in which a synchronization patternof 10 MHz is mixed between signals of 2.4 GHz transmitting othercommunication information, and outputs as a radio signal.

The radio signal output from the communication circuit unit 14A of theprimary power source 1A is demodulated by the communication circuit unit14B (demodulation circuit 140B) of the secondary power source 1B, andthe synchronization pattern of 10 MHz and the other communicationinformation of the 2.4 GHz signals are output.

The demodulation circuit 140B of the secondary power source 1B ispreferably formed as hardware that can demodulate the synchronizationpattern indicating the frequency of the oscillator 121A of the primarypower source 1A at an accurate timing.

Thus, forming the demodulation circuit 140B as the hardware allows adelay during demodulation to be used, for example, as a constant clockdelay Dc, so that the synchronization processing of the PLL circuit 220Bof the secondary power source 1B can be performed accurately.

Accordingly, the second synchronization method described with referenceto FIG. 14A to FIG. 15D has an advantage in that it is unnecessary tostop power transfer of the secondary power source 1B duringsynchronization processing for a second time and thereafter, unlike thefirst synchronization method described with reference to FIG. 13A toFIG. 13C.

In the above description, the method for synchronizing the drivingfrequencies of the LC resonator 11 aA of the primary power source 1A andthe resonator 11 aB of the secondary power source 1B is not limited tothose described above, and obviously, various methods can be applied.

FIG. 16 is a block diagram depicting one example of the wireless powertransfer system of the present embodiment. As depicted in FIG. 16, thepower source 1 includes the wireless power transfer unit 11, the highfrequency power supply unit 12, the power transfer control unit 13, andthe communication circuit unit 14.

The power receiver 2 includes the wireless power reception unit 21, thepower reception circuit unit 22, the power reception control unit 23,the communication circuit unit 24, and the battery unit 25. The powersource 1 and the power receiver 2 communicate with each other throughthe respective communication circuit units 14 and 24 and perform powertransfer by a resonance system (a magnetic field or an electric field)between the wireless power transfer unit 11 and the wireless powerreception unit 21.

FIG. 17 is a block diagram depicting one exemplary power source in thewireless power transfer system. As depicted in FIG. 16 and FIG. 17, inthe power source 1, the wireless power transfer unit 11 includes the LCresonator 11 a and the power supply coil 11 b. The high frequency powersupply unit 12 includes an oscillator 121, an amplifier 122, and amatching device 123.

The power transfer control unit 13 includes a power transfer controlcircuit 131 and a frequency lock circuit 132. The frequency lock circuit132 corresponds to, for example, the PLL circuit 220A and 220B describedwith reference to FIG. 14A to FIG. 14C.

As described above, the frequency lock circuit 132 receives asynchronization signal from the communication circuit unit 14 to performsynchronization processing of the oscillator 121 at a predeterminedinterval (for example, at an interval of from a few minutes to a fewtens of minutes). The oscillator 121 generates a driving signal having afrequency of a predetermined frequency (for example, 6.78 MHz) andoutputs the signal to the wireless power transfer unit 11 (power supplycoil 11 b) through the amplifier 122 and the matching device 123.

The power transfer control circuit 131 includes a CPU (calculationprocessing unit) 134, a memory 135, and an input/output circuit (an I/Ounit) 136 connected to each other by an internal bus 133. The memory 135includes a rewritable non-volatile memory such as a flash memory, a DRAM(Dynamic Random Access Memory), and the like, and executes variouspieces of processing (software programs) of the power source, which willbe described later.

The power source 1 includes, for example, a position sensor S1 detectinga position of the power receiver 2, a human detection sensor (abiodetection sensor) S2 detecting a living body, such as a human or ananimal, and an abnormality detection sensor S3 detecting abnormality ofthe power source 1.

Outputs of the respective sensors S1 to S3 are input to, for example,the CPU 134 through the I/O unit 136 and used in processing inaccordance with a software program (a wireless power transfer program ora power source control program) stored in the memory 135.

The wireless power transfer program (the power source control program)may be stored, for example, in the memory 135 from a portable storagemedium (such as an SD (secure digital) memory card) 70 storing theprogram through the I/O unit 136.

Alternatively, the program may be stored in the memory 135 from a harddisk device 61 of a program (data) provider 60 via a line and the I/Ounit 136. The line from the hard disk device 61 to the I/O unit 136 maybe a wireless communication line using the communication circuit unit14.

In addition, other examples of the portable storage medium (a computerreadable storage medium) storing the wireless power transfer programinclude storage media such as a DVD (digital versatile disk) disk and aBlu-ray disc. Furthermore, FIG. 17 depicts a mere example of the powersource 1, and various changes and modifications can be made.

FIG. 18 is a block diagram depicting one exemplary power receiver in thewireless power transfer system of FIG. 16. As depicted in FIG. 16 andFIG. 18, in the power receiver 2, the wireless power reception unit 21includes the LC resonator 21 a and the power extraction coil 21 b. Thepower reception circuit unit 22 includes a rectifier 221 and a DC-DCconverter 222, and the battery unit 25 includes a battery chargingcontrol LSI 251 and a battery 252.

The power reception control unit 23 includes a CPU (calculationprocessing unit) 234, a memory 235, and an input/output circuit (an I/Ounit) 236. The memory 235 includes a rewritable non-volatile memory suchas a flash memory, a DRAM, and the like, and executes various pieces ofprocessing (software programs) of the power receiver, which will bedescribed later.

The power receiver 2 may be a smart phone, a notebook computer, or thelike that originally includes circuits corresponding to thecommunication circuit unit 14 and the power reception control unit 23,so that such circuits may be usable. Alternatively, for example, thepower reception control unit 23 may be newly provided as a module. Inaddition, when the power receiver 2 does not include circuitscorresponding to the communication circuit unit 14 and the powerreception control unit 23, those circuits will be newly provided.

The power receiver 2 includes, for example, a sensor (athree-dimensional acceleration sensor) SA capable of detecting theposture information (θx, θy, θz) of the power receiver 2. Such anacceleration sensor SA is originally incorporated, for example, in asmart phone or the like, so that the sensor can be used. When the powerreceiver 2 does not include the acceleration sensor SA capable ofdetecting the posture information, it is, for example, possible toperform 2-dimensional charging, although 3-dimensional chargingdescribed above cannot be performed.

Furthermore, even in the power receiver 2, similarly to the power source1, the position sensor S1, the human detection sensor S2, and theabnormality detection sensor S3 may be provided. Alternatively, forexample, only the abnormality sensor S3 may be provided and the otherposition sensor S1 and the human detection sensor S2 may be omitted.

Outputs of the respective sensors SA and S1 to S3 are, for example,input to the CPU 234 through the I/O unit 236 and used in processing inaccordance with a software program (a wireless power transfer program ora power receiver control program) stored in the memory 235.

The wireless power transfer program (the power receiver control program)may be stored, for example, in the memory 235 from a portable storagemedium (such as a micro SD memory card) 90 storing the program throughthe I/O unit 236.

Alternatively, the program may be stored in the memory 235 from a harddisk device 81 of a program (data) provider 80 through a line and theI/O unit 236. The line from the hard disk device 81 to the I/O unit 236may be a wireless communication line using the communication circuitunit 24.

In addition, other examples of the portable storage medium (acomputer-readable storage medium) storing the wireless power transferprogram include storage media such as a DVD disk and a Blu-ray disc.Furthermore, FIG. 18 depicts a mere example of the power receiver 2, andvarious changes and modifications can be made.

Hereinafter, with reference to FIG. 19 to FIG. 24, a description will begiven of processing in the wireless power transfer system of the presentembodiment. In FIG. 19 to FIG. 24, a direction from up to down in eachdrawing represents a flow of time. Additionally, it is assumed that aplurality of power sources (LC resonators: resonance coils) are providedon the power source, although the number of the power sources is notindicated.

Furthermore, even when a single power source includes a plurality of LCresonators, the power source is treated as being equivalent to aplurality of power sources. Accordingly, as in the present embodiment,designating one of a plurality of power sources as a master power sourcemeans that a single calculation processing unit (CPU) controls all theLC resonators included in the master power source and the one or moreslave power sources.

FIG. 19 is a flowchart for illustrating a first example of processing inthe wireless power transfer system of the present embodiment, whichillustrates processing performed when the power source includes aplurality of LC resonators and the power receiver is a single powerreceiver 2. As described above, a single power source 1 may include aplurality of LC resonators 11 a. However, in order to simplifydescription, the description will be given on an assumption that asingle power source 1 has a single LC resonator 11 a.

As depicted in FIG. 19, first, the power source is constantlytransmitting (confirming power transfer partners: ST101), in which aplurality of power sources 1A, 1B, 1C, etc., detect each other (ST102).One of the plurality of power sources is designated as a master powersource 1A and the other ones thereof are designated as slave powersources 1B, 1C, etc., so that the master and the slaves are determined(ST103). In the following processing, all decisions will be made by themaster power source 1A, namely, the CPU 134 of the master power source1A.

In addition, during the constant transmission (confirming the powerreception partner: ST104), the power receiver 2 of the power receiverresponds to communication (authentication check: ST105) and notifies thepower source (the master power source 1A) of necessary power (ST106).

The power source checks the sensor S1 (position sensor) to confirm aposition of the power receiver (ST107), and the power receiver 2confirms a direction thereof by the acceleration sensor SA and transmitsthe confirmed direction (ST108).

The power source determines a relative positional relationship from theconfirmed position (position information) and the direction (postureinformation) transmitted from the power receiver 2, determines anestimated efficiency (ST109), and performs an initial setting ofmatching conditions (ST110).

In addition, the power source (master power source 1A) performs initialsettings of a strength and a phase of each power transfer coil (each ofthe LC resonators of the plurality of power sources 1A, 1B, 1C, etc.)(ST111). Then, the power receiver (power receiver 2) starts preparationof power reception, i.e., turns on the resonance coil (LC resonator) 21a (ST112).

Next, the power source performs a test power transfer (for example, 10%)to confirm the output of 10% (ST113), and checks abnormality by thesensor S3 (abnormality detection sensor), i.e., confirms no abnormalheat generation (ST114). The output of 10% in the test power transfer isa mere example and the output of the test power transfer is not limitedthereto. At this time, the power receiver 2 confirms power reception andtransmits that the power reception has been done (ST115).

The power source calculates efficiency from the power reception and thepower transfer and confirms whether the efficiency is within theestimated efficiency (ST116). In addition, the power source checks thesensor S2 (human detection sensor) and performs power transfer in asmall power mode when a person is present (ST117), whereas performs afull power transfer (100% power transfer) when no person is present toconfirm the output of 100% (ST118).

Additionally, the power source checks the sensor S3 (abnormalitydetection sensor) to confirm that there is no abnormal heat generation(ST119). The abnormal detection sensor S3 may be provided either in thepower source 1 or the power receiver 2. When the abnormality detectionsensor S3 is provided in the power receiver 2, the presence or absenceof abnormal heat generation confirmed by the abnormality detectionsensor S3 will be transmitted to the master power source 1A.

The power receiver 2 confirms power reception and transmits that thepower reception has been done (ST120). The power source calculatesefficiency from the power reception and the power transfer and confirmswhether the efficiency is within the estimated efficiency (ST121). Inother words, power transfer efficiency can be calculated from powertransmitted from the power source (all the power sources 1A, 1B, etc.,)and power received by the power receiver 2. The power source confirmswhether the calculated efficiency is within the efficiency estimated inadvance. When the calculated efficiency is not within the estimatedefficiency, the power source decides, for example, that somethingabnormal has occurred and executes power transfer stop, alarmgeneration, abnormality display, and the like.

FIG. 20 is a flowchart for illustrating a second example of processingin the wireless power transfer system of the present embodiment, whichillustrates processing performed when the power source includes aplurality of power sources 1A, 1B, 1C, etc., and the power receiverincludes two power receivers 2A and 2B.

As depicted in FIG. 20, first, the power source is constantlytransmitting (confirming a power transfer partner: ST201). In the powerreceiver, the power receiver 2A responds to the communication(authentication check) and notifies necessary power (ST202), and thepower receiver 2B responds to the communication (authentication check)and notifies necessary power (ST203).

The power source checks the sensor S1 (position sensor) to confirmpositions of the respective power receivers 2A and 2B (positioninformation) (ST204). In addition, in the power receiver, the powerreceiver 2A confirms a direction thereof (posture information) by theacceleration sensor SA and transmits the confirmed direction (ST205),and the power receiver 2B confirms a direction thereof (postureinformation) by the acceleration sensor SA and transmits the confirmeddirection (ST206).

The power receiver determines a relative positional relationship fromthe position (position information) and the direction (postureinformation) to determine each estimated efficiency (ST207). Inaddition, the power receiver performs an initial setting of matchingconditions (ST208) and performs initial settings of a strength and aphase of each power transfer coil (ST209).

Then, the power receiver 2A starts preparation of power reception, i.e.,turns on the resonance coil 21 aA (ST210). The power source performs atest power transfer (for example, 10%) to confirm the output of 10%(ST211), and checks abnormality by the sensor S3 (abnormality detectionsensor), i.e., confirms no abnormal heat generation (ST212). Asdescribed above, the abnormality detection sensor S3 may be provided inthe power receivers 2A and 2B.

At this time, the power receiver 2A confirms power reception, thentransmits that the power reception has been done, and turns off theresonance coil 21 aA (ST213). The power source calculates efficiencyfrom the power reception and the power transfer and confirms whether theefficiency is within the estimated efficiency 1 (ST214).

Next, the power receiver 2B starts preparation of power reception, i.e.,turns on the resonance coil 21 aA (ST215). The power source performs atest power transfer (for example, 10%) to confirm the output of 10%(ST216), and checks abnormality by the sensor S3 (abnormality detectionsensor), i.e., confirms no abnormal heat generation (ST217).

At this time, the power receiver 2B confirms power reception, thentransmits that the power reception has been done, and turns off theresonance coil 21 aB (ST218). The power source calculates efficiencyfrom the power reception and the power transfer and confirms whether theefficiency is within the estimated efficiency 2 (ST219).

In this manner, the present embodiment performs the test power transferin turn to the plurality of power receivers 2A and 2B to confirm thepresence or absence of abnormality and then calculates distributionconditions for the plurality of power receivers 2A and 2B, as well asperforms resonance adjustments (fine adjustments) described withreference to FIG. 8E to FIG. 8H, thereby allowing for simultaneoustransmission.

Specifically, when the test power transfer to the plurality of powerreceivers 2A and 2B is ended, the power source calculates distributionconditions and transmits to the respective power receivers 2A and 2B(perform power transfer: ST220). Then, the power receiver 2A startspreparation of power reception, i.e., turns on the resonance coil 21 aAand performs fine adjustment (ST221). The power receiver 2B startspreparation of power reception, i.e., turns on the resonance coil 21 aBand performs fine adjustment (ST222).

The power source performs test power transfers (for example, 10%) toconfirm the output of 10% (ST223), and checks abnormality by the sensorS3 (abnormality detection sensor), i.e., confirms no abnormal heatgeneration (ST224). The power receiver confirms power receptions of thepower receivers 2A and 2B and transmits that the power receptions havebeen done (ST225).

The power source calculates efficiencies from the power receptions andthe power transfers and confirms whether the efficiencies are within theestimated efficiencies 1 and 2 (ST226). In addition, the power sourcechecks the sensor S2 (human detection sensor) and performs powertransfer in a small power mode when there is a person (ST227), whereasperforms a full power transfer (100% power transfer) when there is noperson and confirms the output of 100% (ST228).

Additionally, the power source checks the sensor S3 (abnormalitydetection sensor) to confirm that there is no abnormal heat generation(ST229). The power receiver confirms power reception and transmits thatthe power reception has been done (ST230), and the power sourcecalculates efficiencies from the power receptions and the powertransfers to confirm whether the efficiencies are within the estimatedefficiencies (ST231).

As described above, when the calculated efficiencies are not within theestimated efficiencies, the power source performs, for example, powertransfer stop, alarm generation, abnormality display, and the like.Furthermore, the same processing will be performed also in similarconfirmations on being within estimated efficiencies that will bedescribed below.

FIG. 21 is a flowchart for illustrating a third example of processing inthe wireless power transfer system of the present embodiment, whichillustrates processing by the sensor S2 (human detection sensor orbiodetection sensor).

As depicted in FIG. 21, the power source confirms the output of 100%(ST301) and checks the sensor S3 (abnormality detection sensor) toconfirm that there is no abnormal heat generation (ST302). Then, thepower receiver confirms the power receivers 2A and 2B and transmits thatthe power receptions have been done (ST303).

The power source calculates efficiencies from the power receptions andthe power transfers to confirm whether the efficiencies are within theestimated efficiencies (ST304). In addition, the power source checks thesensor S2 (human detection sensor) to confirm that there is no person(ST305) and then checks the sensor S1 (position sensor) to confirmpositions of the power receivers (ST306).

FIG. 22 is a flowchart for illustrating a fourth example of processingin the wireless power transfer system of the present embodiment, whichillustrates processing performed after completion of a predeterminedamount of charging in a power receiver.

As depicted in FIG. 22, upon completion of a predetermined amount ofcharging (ST401), the power receiver (power receiver) requests powertransfer stop and transmits the power transfer stop request (ST402). Thepower source receives the power transfer stop from the power receiver(ST403) and stops power transfer (ST404). Then, the power receiverconfirms power reception stop (ST405) and turns off the resonance coil(ST406).

FIG. 23 is a flowchart for illustrating a fifth example of processing inthe wireless power transfer system of the present embodiment, whichillustrates processing performed after completion of a predeterminedamount of charging in one of the two power receivers.

As depicted in FIG. 23, upon completion of a predetermined amount ofcharging in the power receiver 2A (ST501), the power receiver 2Arequests power transfer stop and transmits the power transfer stoprequest (ST502). At this time, it is assumed that the power receiver 2Bhas not completed a predetermined amount of charging.

The power source receives the power transfer stop from the powerreceiver 2A (ST503) and temporarily stops power transfer (ST504). Then,the power receivers 2A and 2B confirm power reception stop (ST505), andthe power receiver 2A turns off the resonance coil 11 aA (ST506). Thepower source restarts power transfer in order to perform power transferto the power receiver 2B (performs power transfer start operationsincluding a test power transfer: ST507).

FIG. 24 is a flowchart for illustrating a sixth example of processing inthe wireless power transfer system of the present embodiment, whichillustrates processing performed for a device with a battery residualcapacity of zero. The processing for the device with a battery residualcapacity of zero does not use information given by the position sensorS1 and the acceleration sensor SA.

As depicted in FIG. 24, during power transfer to each device by thepower source (ST601), each device of the power receiver is receivingpower (ST602). Next, a user places a device (power receiver) with abattery residual capacity of zero near the power sources (ST603). Aposition at which the power receiver with the battery residual capacityof zero is placed near the power sources is a predetermined powerreception position designated in advance.

Furthermore, the user turns on the battery residual capacity zero switch(ST604), whereby the power source stops power transfer (ST605) andcommunicates turning off of the resonance coils to the entire powerreception system (the power receivers) (ST606). The power receiver turnsoff the resonance coils of all the power receivers (all the powerreceivers except for the power receiver with the battery residualcapacity of zero) (ST607).

The power source (master power source) decides that the power receiverwith the battery residual capacity of zero is located at thepredetermined position, then estimates a relative positionalrelationship (ST608), and performs an initial setting of matchingconditions (ST609). In other words, the power source transmits power tothe power receiver with the battery residual capacity of zero, forexample, using electromagnetic induction coupling.

In addition, the power source performs initial settings of a strengthand a phase of each power transfer coil (ST610), then performs a testpower transfer (for example, 10%) to confirm the output of 10% (ST611),and checks abnormality by the sensor S3 (abnormality detection sensor),i.e., confirms no abnormal heat generation (ST612).

The master power source checks the sensor S2 (human detection sensor)and performs power transfer in a small power mode when there is a person(ST613), and performs a full power transfer RT1 (for example, 5 W) whenthere is no person and confirms the output of 5 W (ST614). Then, themaster power source checks abnormality by the sensor S3 (abnormalitydetection sensor), i.e., confirms no abnormal heat generation (ST615).

Next, the master power source continues the full power transfer RT1 (forexample, 5 W) for a predetermined time (for example, about 5 minutes) toconfirm communication to the power receivers (ST616). This confirmationmay be made by checking impedance stability (ST617). In the powerreceiver (the power receiver with the battery residual capacity ofzero), for example, when charging is insufficient, communication remainsimpossible (ST618).

Furthermore, the master power source performs a full power transfer RT2(for example, 10 W) to confirm the output of 10 W (ST619), and checksabnormality by the sensor S3 (abnormality detection sensor), i.e.,confirms no abnormal heat generation (ST620).

Then, the master power source continues the full power transfer RT2 (forexample, 10 W) for a predetermined time (for example, about 5 minutes)to confirm communication to the power receivers (ST621). Thisconfirmation may be made by confirming impedance stability (ST622). Inthe power receiver (the power receiver with the battery residualcapacity of zero), for example, when charging proceeds, the powerreceiver whose battery residual capacity had been zero responds tocommunication (ST623).

The power source continues ordinary power transfer to a single powerreceiver only for a predetermined time (ST624). Power transfer to thepower receiver with the battery residual capacity of zero may beperformed until full charging of the battery is completed by powertransfer using electromagnetic induction. However, alternatively, afterthe charging proceeds to some extent (up to a communicable level), thepower transfer may be switched to a power transfer using resonance.

Then, the power source stops power transfer (ST625) and restartsprocessing from starting of ordinary power transfer (ST626), i.e.,executes processing described with reference to FIG. 19 to FIG. 23described above.

While the embodiment has been described above, all examples andconditional language recited herein are intended to aid the reader inunderstanding the concept of the present invention applied to theinvention and the technique. Such specifically recited examples andconditions are not to be construed as limiting the scope of theinvention nor do the configurations of the examples herein indicatemerits and demerits of the invention. Although the embodiment of theinvention has been detailed, it is to be understood that variouschanges, replacements, and modifications can be made thereto withoutdeparting from the spirit and the scope of the invention.

All examples and conditional language provided herein are intended forthe pedagogical purposes of aiding the reader in understanding theinvention and the concepts contributed by the inventor to further theart, and are not to be construed as limitations to such specificallyrecited examples and conditions, nor does the organization of suchexamples in the specification relate to a showing of the superiority andinferiority of the invention. Although one or more embodiments of thepresent invention have been described in detail, it should be understoodthat the various changes, substitutions, and alterations could be madehereto without departing from the spirit and scope of the invention.

What is claimed is:
 1. A wireless power transfer system comprising: aplurality of power sources; and a power receiver, power transfer from atleast one of the plurality of power sources to the power receiver beingperformed in wireless by using magnetic field resonance or electricfield resonance, wherein each of the plurality of power sourcesincludes: a power supply unit; a wireless power transfer unit includinga first LC resonator configured to receive power from the power supplyunit and wirelessly transmit the power to the power receiver; and apower transfer control unit configured to control the power supply unitand the wireless power transfer unit, wherein the power transfer controlunit controls the first LC resonator so as not to operate ordinarily. 2.The wireless power transfer system as claimed in claim 1, wherein eachof the plurality of power sources includes a switch configured tocontrol an on-state or off-state of resonance of the first LC resonator,wherein the power transfer control unit controls the switch so as not tooperate the first LC resonator ordinarily.
 3. The wireless powertransfer system as claimed in claim 1, wherein each of the plurality ofpower sources includes a wireless power transfer unit configured towirelessly transmit power by using magnetic field resonance or electricfield resonance, and the power receiver includes a wireless powerreception unit configured to receive the power wirelessly transmitted byusing the magnetic field resonance or the electric field resonance. 4.The wireless power transfer system as claimed in claim 1, wherein thepower receiver includes a wireless power reception unit including asecond LC resonator, a power reception circuit unit configured toextract power from the wireless power reception unit, and a powerreception control unit configured to control the power reception circuitunit, wherein the power reception control unit controls the second LCresonator so as not to operate ordinarily.
 5. The wireless powertransfer system as claimed in claim 4, wherein the first LC resonatordirectly receives a first power from the power supply unit, or the firstLC resonator receives the first power from the power supply unit via apower supply coil, the power supply coil receiving the first power fromthe power supply unit and supplying the first power by usingelectromagnetic induction to the first LC resonator.
 6. The wirelesspower transfer system as claimed in claim 4, wherein the second LCresonator directly supplies a second power to a load or a power supplyof the power receiver, or the second LC resonator supplies the secondpower to the load or the power supply of the power receiver via a powerextraction coil, the power extraction coil receiving the second power byusing electromagnetic induction from the second LC resonator and supplythe second power to the load or the power supply of the power receiver.7. The wireless power transfer system as claimed in claim 1, whereineach of the plurality of power sources includes a first communicationcircuit unit configured to perform communication with other one or moreof the power sources of the plurality of power sources and with thepower receiver; and the power receiver includes a second communicationcircuit unit configured to perform communication with the plurality ofpower sources.
 8. The wireless power transfer system as claimed in claim1, wherein when the power receiver is a power receiver with a batteryresidual capacity of zero, the power receiver with the battery residualcapacity of zero is arranged in contact with one of the plurality ofpower sources.
 9. The wireless power transfer system as claimed in claim1, wherein each of the plurality of power sources includes an oscillatorand a synchronization circuit; and when the plurality of power sourcesperform the power transfer to the power receiver, one of the pluralityof power sources is designated as a primary power source and the otherone or more power sources are designated as secondary power sources; theprimary power source performs the power transfer according to afrequency of the oscillator; and the secondary power sources synchronizethe synchronization circuits of the secondary power sources with thefrequency of the oscillator of the primary power source to perform thepower transfer according to a frequency of the synchronization circuitsof the secondary power sources in which the frequency has beensynchronized therewith.
 10. A wireless power transfer method comprisinga plurality of power sources and a power receiver, in which powertransfer from at least one of the plurality of power sources to thepower receiver is performed in wireless by using magnetic fieldresonance or electric field resonance, each of the plurality of powersources including a power supply unit; a wireless power transfer unitincluding a first LC resonator configured to receive power from thepower supply unit and wirelessly transmit the power to the powerreceiver; and a power transfer control unit configured to control thepower supply unit and the wireless power transfer unit, wherein thewireless power transfer method comprising: controlling, by the powertransfer control unit, the first LC resonator so as not to operateordinarily.
 11. The wireless power transfer method as claimed in claim10, wherein each of the plurality of power sources includes a switchconfigured to control an on-state or off-state of resonance of the firstLC resonator, wherein the power transfer control unit controls theswitch so as not to operate the first LC resonator ordinarily.
 12. Thewireless power transfer method as claimed in claim 10, wherein when thepower receiver is a power receiver with a battery residual capacity ofzero, arranging the power receiver with the battery residual capacity ofzero in contact with one of the plurality of power sources.
 13. Thewireless power transfer method as claimed in claim 10, wherein the powerreceiver includes a wireless power reception unit including a second LCresonator, a power reception circuit unit configured to extract powerfrom the wireless power reception unit, and a power reception controlunit configured to control the power reception circuit unit, wherein thepower reception control unit controls the second LC resonator so as notto operate ordinarily.
 14. The wireless power transfer method as claimedin claim 13, wherein the first LC resonator directly receives a firstpower from the power supply unit, or the first LC resonator receives thefirst power from the power supply unit via a power supply coil, thepower supply coil receiving the first power from the power supply unitand supplying the first power by using electromagnetic induction to thefirst LC resonator.
 15. The wireless power transfer method as claimed inclaim 13, wherein the second LC resonator directly supplies a secondpower to a load or a power supply of the power receiver, or the secondLC resonator supplies the second power to the load or the power supplyof the power receiver via a power extraction coil, the power extractioncoil receiving the second power by using electromagnetic induction fromthe second LC resonator and supply the second power to the load or thepower supply of the power receiver.
 16. The wireless power transfermethod as claimed in claim 10, wherein each of the plurality of powersources includes an oscillator and a synchronization circuit; and whenthe plurality of power sources perform the power transfer to the powerreceiver, one of the plurality of power sources is designated as aprimary power source and the other one or more power sources aredesignated as secondary power sources; the primary power source performsthe power transfer according to a frequency of the oscillator; and thesecondary power sources synchronize the synchronization circuits of thesecondary power sources with the frequency of the oscillator of theprimary power source to perform the power transfer according to afrequency of the synchronization circuits of the secondary power sourcesin which the frequency has been synchronized therewith.